Concrete construction and other work requiring on-the-job transport of heavy materials from one location to another has brought about the development of a variety of relatively-small, load-carrying vehicles capable of moving on the job site with relatively small but often very heavy loads of material. For example, a frequent need is to load a quantity of concrete at a first location, transport such concrete to a second location and then dump the contents for spreading and screeding operations at the second location. In concrete work such vehicles are often referred to as a "concrete buggy". They may also be referred to as a dump truck or power-driven wheelbarrow. Some of such vehicles are of the walk-behind type while others are of the step or seat-riding type. The load which is carried by a container called a "skip", "hopper", "pan", or "dump box" is conventionally raised and lowered by a hydraulic piston as in U.S. Pat. Nos. 2,424,670 or 2,427,132. A front pair of single or dual wheels is conventionally driven by a differential and transmission as in U.S. Pat. No. 2,427,132. In the three-wheel-type vehicle, a single or dual wheel supports the rear of the vehicle and is adapted for rotating around a vertical axis for the purpose of steering the vehicle and sometimes with use of a steering mechanism as in U.S. Pat. No. 2,427,132. The conventional way of braking the vehicle is by use of mechanical brakes as illustrated in U.S. Pat. Nos. 2,427,132 and 2,530,574.
With the above brief description of those aspects of the concrete buggy-type prior art apparatus deemed pertinent to the present invention, it will be immediately apparent that there is a continuing need for improvements in the manner in which a vehicle of this type is driven as well as in the manner of braking the vehicle, particularly when carrying a heavy load. While mechanical drive systems have prevailed, it has been known to employ a hydraulic drive motor for driving a single rear wheel instead of mechanically driving two front wheels as is the conventional practice. In this regard, the Prime-Mover Company of Muscatine, Iowa 52761, has made a three-wheel vehicle for handling packaged or palletized brick or block and sold as the L-32 and L-36 models of what is referred to as a "straddle-type mason tender". In the hydraulic system employed in the Prime-Mover apparatus both forward and reverse action as well as braking action are said to be achieved with a single hydraulic drive motor. However, except for this type of three-wheel vehicle in which a single rear wheel is driven by a single hydraulic drive motor, applicant is unaware of any other attempts that have been made to use hydraulic drive motors for driving three wheel concrete buggy type vehicles.
The present invention seeks to improve upon the aforementioned prior art by providing in a motorized so-called "three-wheel-type dump vehicle" a hydraulic drive system for the front wheels, with means in the hydraulic system enabling the front wheels to act as brakes and also with means whereby the hydraulic fluid can be cooled within a reservoir which acts both as a structural frame member and as a uniquely-arranged heat sink in which the concrete or other relatively-cool material being transported is used to absorb heat from the hydraulic fluid. In other aspects, the invention also seeks to provide an improved hydraulic system enabling both the dump box as well as the front wheels to be hydraulically operated and with a minimum requirement of horsepower in the gasoline engine used as the prime source of power for the vehicle. Other objects will become apparent as the description proceeds.